the initial velocity plots of the enzyme follow the Michaelis-Menten equation in the absence of NADH. In its presence, however, the velocity versus substrate plots for NADP+ become sigmoidal but remain hyperbolic for glucose 6-phosphate as the variable substrate. Inhibition against both of the substrates of the enzyme by NADH is noncompetitive. The inhibition curves for NADH are also sigmoidal, suggesting a multisite binding of the inhibitor on the enzyme surface